Abstract: Proteomic Analysis of Highly Malignant Bladder Transitional Cell Carcinoma and Verificationof MortalinLi ZHAO1, Shumin ZHANG2, Yuanyuan ZHAO1, Jiwu CHANG2Corresponding author: Shumin ZHANG, E-mail: zhangshuminhh@yahoo.com.cn1Department of Pathology, Tianjin Children's Hospital, Tianjin 300074, China2Tianjin Institute of Urology, Tianjin 300211, ChinaAbstract Objective: To investigate the differences in protein expression profiles between highly malignant bladder transitionalcell carcinoma (BTCC) and normal urothelial cells and to verify the differentially expressed proteins that might be potential and valu-able biomarkers for BTCC. Methods: The proteins expressed in highly malignant BTCC and normal urothelial cells were separated byhand microdissection combining two-dimensional electrophoresis (2-DE), and then identified by matrix-assisted laser desorption ioniza-tion time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). Semi-quantitative RT-PCR and immunohistochemistrywere employed for further verification, Results: A total of 11 differentially expressed proteins were identified and five of them includ-ing cytoskeletal 7, 60 kDa heat shock protein, cytoskeletal 8, annexin A5 and prohibitin were reported possibly correlated with the de-velopment of BTCC. The other 6 proteins were mortalin, 14-3-3 protein epsilon, protein disulfide-isomera-se A6, annexin A4, desminand tubulin beta-3 chain. Semi-quantitative RT-PCR and immunohistochemistry showed that the screened protein mortalin was up-regu-lated in highly malignant BTCC ( P < 0.01 ). Conclusion: The protein profile of highly malignant BTCC is obviously different fromthat of normal urothelial cells, indicating involvement of various distinct proteins in bladder carcinogenesis. The identified protein mor-talin might be a potential and valuable biomarker for bladder transitional cell carcinoma.Keywords Highly malignant bladder transitional cell carcinoma; Microdissection two-dimensional electrophoresis;MALDI-TOF/TOF-MS; Mortalin